Dual-side antireflection coatings for broad angular and wavelength bands

Abstract

A waveguide display includes a first substrate having two opposing sides, a grating on a first side of the two opposing sides of the first substrate and configured to couple display light into or out of the first substrate, a first antireflection layer on a first surface of the grating and configured to reduce reflection of visible light at the first surface of the grating, and a second antireflection layer on a second side of the two opposing sides of the first substrate and configured to reduce reflection of the visible light at the second side of the first substrate.

What is claimed is: 
     
         1 . A waveguide display comprising:
 a first substrate including two opposing sides;   a grating on a first side of the two opposing sides of the first substrate, the grating configured to couple display light into or out of the first substrate;   a first antireflection layer on a first surface of the grating and configured to reduce reflection of visible light at the first surface of the grating; and   a second antireflection layer on a second side of the two opposing sides of the first substrate and configured to reduce reflection of the visible light at the second side of the first substrate.   
     
     
         2 . The waveguide display of  claim 1 , wherein at least one of the first antireflection layer or the second antireflection layer includes an array of micro-structures. 
     
     
         3 . The waveguide display of  claim 2 , wherein the micro-structures include vertical ridges, pillars, tapered ridges, or cones. 
     
     
         4 . The waveguide display of  claim 2 , wherein the array of micro-structures is in a material layer characterized by a first refractive index lower than a second refractive index of the first substrate. 
     
     
         5 . The waveguide display of  claim 2 , wherein the array of micro-structures includes a one-dimension or two-dimensional array of micro-structures. 
     
     
         6 . The waveguide display of  claim 2 , wherein a period of the array of micro-structures is less than a half of a period of the grating. 
     
     
         7 . The waveguide display of  claim 1 , wherein the first antireflection layer has a reflectivity less than 5% for visible light with incident angles less than 75°. 
     
     
         8 . The waveguide display of  claim 1 , wherein the first antireflection layer or the second antireflection layer includes two or more layers characterized by different respective effective refractive indices less than a refractive index of the first substrate. 
     
     
         9 . The waveguide display of  claim 1 , wherein the grating includes one or more grating layers configured to cause destructive interference between ambient light diffracted by at least two grating layers or between ambient light diffracted by different portions of one grating layer. 
     
     
         10 . The waveguide display of  claim 1 , wherein the grating includes:
 a slanted grating including a plurality of slanted ridges, the slanted grating characterized by a height, a period, and a slant angle of the plurality of slanted ridges configured to cause destructive interference between ambient light diffracted by different portions of the slanted grating; or   at least two grating layers, wherein the at least two grating layers are characterized by a same grating period and are offset by a half of the grating period.   
     
     
         11 . The waveguide display of  claim 1 , further comprising a second grating between the first substrate and the second antireflection layer. 
     
     
         12 . The waveguide display of  claim 11 , wherein the grating and the second grating are configured to diffract display light of different respective colors or display light for different respective fields of view. 
     
     
         13 . The waveguide display of  claim 1 , further comprising:
 a second substrate;   a second grating on a first side of the second substrate and configured to couple display light into or out of the second substrate, the grating and the second grating configured to diffract display light of different respective colors or display light for different respective fields of view;   a third antireflection layer on a first surface of the second grating and configured to reduce reflection of the visible light at the first surface of the second grating; and   a fourth antireflection layer on a second side of the second substrate opposing the second grating and configured to reduce reflection of the visible light at the second side of the second substrate.   
     
     
         14 . The waveguide display of  claim 1 , further comprising:
 a second substrate;   a second grating on a first side of the second substrate and configured to diffract invisible light;   a third antireflection layer on a first surface of the second grating and configured to reduce reflection of the visible light at the first surface of the second grating; and   a fourth antireflection layer on a second side of the second substrate opposing the second grating and configured to reduce reflection of the visible light at the second side of the second substrate.   
     
     
         15 . The waveguide display of  claim 1 , further comprising an angular-selective transmissive layer configured to reflect, diffract, or absorb ambient light incident on the angular-selective transmissive layer with an incidence angle greater than a threshold value. 
     
     
         16 . The waveguide display of  claim 1 , wherein the first substrate includes a curved substrate. 
     
     
         17 . A near-eye display comprising:
 a waveguide including a first surface and a second surface opposing the first surface;   an input coupler configured to couple display light from an image source into the waveguide;   an output coupler coupled to the first surface of the waveguide and configured to:
 refractively transmit ambient light; and 
 diffractively couple the display light out of the waveguide; 
   a first antireflection layer for visible light on the output coupler; and   a second antireflection layer for visible light on the second surface of the waveguide.   
     
     
         18 . The near-eye display of  claim 17 , wherein the first antireflection layer includes an array of micro-structures in a material layer characterized by a first refractive index lower than a second refractive index of the waveguide or the output coupler. 
     
     
         19 . The near-eye display of  claim 18 , wherein:
 the array of micro-structures includes a one-dimensional or two-dimensional array of ridges, pillars, tapered pillars, or cones; and   a period of the array of micro-structures is less than a half of a period of the output coupler.   
     
     
         20 . The near-eye display of  claim 17 , wherein the output coupler comprises one or more grating layers and is configured to cause destructive interference between ambient light diffracted by at least two grating layers or between ambient light diffracted by different portions of one grating layer.